Jupiter And Longevity

For the reason why James Blish's characters, unlike Poul Anderson's and Clifford Simak's, do not adapt human beings to live on Jupiter, see On Jupiter. And to reiterate:

"'We've sense enough - or humility enough, if you like that better - to know that we can't adapt men to a planet like Jupiter...'"

-James Blish, "Surface Tension" IN Blish, The Seedling Stars (London, 1972), pp. 107-180 AT p. 109.

However, in the stories in question, Anderson and Simak had still been thinking of Jupiter merely as a bigger planet with a solid surface whereas Blish was working with the updated idea of a "gas giant," a large planet with a turbulent atmosphere merely densening but never solidifying all the way down to the eventual planetary core.

Sf writers discuss the same questions but give different answers:

Heinlein's Howard Families breed for longevity; 

Blish's characters say that this is impossible but develop antiagathic drugs;

Anderson has antisenescence in the Technic History, anti-aging treatment in the Time Patrol and three different kinds of immortality in other works.